A dual fuel engine is designed to run on more than one fuel, for example, a liquefied gas-diesel mixture. In such engines, a relatively small quantity of injected liquid diesel fuel is compression ignited, which, in turn, ignites a relatively larger charge of natural gas. In a dual fuel compression ignition engine, the ratio of substituted natural gas may be limited by abnormal combustion conditions, such as abnormal detonation (i.e., engine knock), which is generally dependent on intake manifold air temperature (IMAT), among various other boundary conditions, such as cylinder temperature, gas-diesel mixture temperature, cylinder compression, etc. The dual fuel compression ignition engine, using diesel and natural gas, can be sensitive to IMAT, which may limit the amount of natural gas available for combustion.
International Publication No. WO 2013/047574, hereafter the '574 publication, describes a direct-injection diesel engine system that uses a high-pressure gas generated by vaporizing a low-temperature liquid fuel as an engine fuel, and that combusts the engine fuel with intake air pressurized by a supercharger. According to the '574 publication, the direct-injection diesel engine system includes a cooling-energy recovery heat exchanger that conducts heat exchange between a heat medium that circulates through a closed circuit and high-pressure low-temperature liquid fuel pressurized by a booster pump to cool the heat medium, and an air-cooling heat exchanger that conducts heat exchange with the heat medium downstream of the cooling-energy recovery heat exchanger to cool air which is to be supplied to the supercharger and used as intake air and/or to cool intake air compressed by the supercharger. However, the '574 publication is not understood to recite selectively providing coolant of a separate circuit aftercooler (SCAC) system to a vaporizer to vaporize low-temperature liquid fuel.